Alastair Grant - WPA Pool/Getty Images(LONDON) -- America's top diplomat suggested in a passing remark Monday that Syrian President Bashar al-Assad could avoid a U.S.-led strike if he handed over all his chemical weapons, but the State Department quickly dismissed the comment as more of a "rhetorical argument" than an offer.

In a London news conference Monday morning, Secretary of State John Kerry responded to a question about whether Assad could do anything to avoid war by saying "he could turn over every single bit of his chemical weapons to the international community in the next week. Turn it over, all of it, without delay and allow a full and total accounting."

Kerry delivered the statement almost dismissively and quickly said Assad had no intention giving up "weapons he denies using." But it was still the first time such a suggestion had been made by the Obama administration.

The State Department was forced to clarify the remarks, calling them rhetorical and making clear its desire to strike could be tempered by a Syrian offer. Kerry's point, according to spokeswoman Jen Psaki, "was that this brutal dictator with a history of playing fast and loose with the facts cannot be trusted to turn over chemical weapons."

Kerry also rebutted new claims by Assad that the United States has no proof the Syrian president personally ordered the chemical weapons attack.

In an interview with PBS' and CBS' Charlie Rose, Assad argued that Kerry had not presented a "single shred of evidence." The German magazine Bild seemed to give some credence to Assad's claims this weekend, reporting that Syrian government forces might have carried out the Aug. 21 chemical weapons attack without Assad's permission.

In response, Kerry argued that Syrian chemical weapons are tightly controlled and that there is "no question about responsibility."

"The chemical weapons in Syria we have tracked for some period of time now are controlled in a very tight manner by the Assad regime," Kerry said. "Under any circumstances, the Assad regime is the Assad regime. "The regime issues orders, and we have high-level regime [members] who have been caught issuing these instructions, with the results going directly to President Assad."

He later added: "What does [Assad] offer? Words that are contradicted by fact."

Kerry, as he has done for the past week, also tried to walk a fine line between sounding a battle cry in Syria and claiming the United States was "not going to war," -- a reflection of how difficult the Obama administration is finding it to sell an attack on Syria.

When arguing for the need to strike, Kerry compared the chemical weapons attacks to the Holocaust, which killed more than six million, and the Rwandan genocide, during which almost one million people died in the 1990s.

"If one party believes he can rub out countless numbers of his own citizens with chemical weapons, he will never get to the negotiation table," Kerry argued. "A resolution will never get done on the battlefield. It will be done at the negotiating table. But we have to get to that table."

But at the same time, he also tried to downplay the scope of the U.S. plans, saying an attack was not an act of war.

"We're not talking about war. We are not going to war," Kerry said. "We are going to be able to hold Bashar Assad accountable, in a very limited, very targeted, very short-term effort that degrades his capacity to deliver chemical weapons without assuming responsibility for Syria's Civil War."

A small group of protestors outside the British foreign office disagreed, holding up signs that said, "Hands Off Syria."

"One, two, three four," they chanted, "we don't want another war."

After the news conference, Kerry left for Washington to lobby Congress to authorize the military strike in Syria.